Reactive Chemistry

TECHNICAL INFORMATION

Murat ŞAHİNLİ
12.11.2015
Cellulose… Cellulose structure
Reactive dyes… General structure

has a reactive group which are adsorbed on to the cellulose and than reacted with the
fiber to form covalent bonds.

Chromophore Bridging RG

Reactive group

Functional groups
 Reactive dyes… General structure

has a reactive group which are adsorbed on to the cellulose and than reacted with the
fiber to form covalent bonds.

Chromophore Bridging RG

Functional groups

Shade Fastness
Fastness Dischargeability
Levelness Fixation
Substantivity Application temperature
Solubility
Application temperature
Reactive dyes… General reaction

When put fabric and dye into the water;

Cellulose: Cell-OH Cell-O¯

Electrostatic
repulsion because of
Dye: the negative charges
HO3S-Dye-X X-Dye-SO3¯

With addition of salt: Cell-O¯ ⁺ Na

Reduce the repulsion
X-Dye-SO3¯ ⁺ Na
Reactive dyes… General reaction

After addition alkaline and linking with covalent bond;

Thanks to covalent bond

X-Dye-SO3¯ ⁺ Na + Na ⁺ ¯O-Cell
Linking much more resistant to the
usual conditions of use than the
( Soda ash, caustic …) physicochemical bond between
direct dyes and cellulose.

Na ⁺ ¯O3S – Dye –O-Cell + NaX Bond type App. Relative strength

Covalent 30.0

Ionic 7.0

Hydrogene 3.0
Other
1.0
Intermolecular
Reactive dyes… Description of dyeing mechanism

 Exhaustion of dye in presence of electrolyte by adsorption

 Fixation under the influence of alkali

 Wash off the unfixed dye from material surface

T1: Addition of
alkali and start of
the fixation
 Reactive dyes… Exhaustion

 The reactive dyes is adsorbed onto the cellulose surface and than diffuses into the fiber.
 This phase is fully reversible.
 Dye molecules are in equilibrium between fiber and dyebath.

Any change in bath composition

affect the equilibrium

[F] Dyebath [F] Cellulose

So; affect the Substantivity

[F] Cellulose
S= [F] Dyebath
Reactive dyes… Substantivity: Influencing parameters

pH
Electrolyte Temperature
conc.

Dye conc. Type of fiber

Dye Liquor
Substantivity
affinity ratio
 Reactive dyes… Substantivity: Influencing parameters

Standart affinity of dye;

Like substantivity; is a measure for the distribution of a dye between fiber and dyebath.
Unlike substantivity; affinity is constant at dyeing conditions, it is dye-spesific characteristic.

The number of
conjugated double Substantivity
High affinity for cellulose (Direct dye)
bonds in chromophore

Low affinity for cellulose (Acid dye)

 Reactive dyes… Substantivity: Influencing parameters

Electrolyte Concentration;

Electrolyte conc. Anion-anion repulsion Substantivity

Direct dyes; high affinity, require 5-10 g/lt salt

Reactive dyes; medium to low affinity, require 40-100 g/lt
 Reactive dyes… Substantivity: Influencing parameters

pH of dyebath;
OH¯
Cell-OH Cell-O¯ + H2O
H⁺

As the pH increases, the cellulose carries more and more negatively charge.
The amount of the OH ion in the dye bath increases.

pH Substantivity
7
8
9
Cell-O¯ (in the fiber)
10
RS:
11 OH¯ (in the dyebath)
12
13

Without alkaline addition

 Reactive dyes… Substantivity: Influencing parameters

Dye concentration;

Because of the limited adsorption

capacity of fiber surface;

[F] Cellulose
S= [F] Dyebath

Dye concentration Substantivity

Surface saturation occurs later with high affinity dyes

than low affinity dyes so,

the greater influence on substantivity of low affinity

dyes
 Reactive dyes… Substantivity: Influencing parameters

Dyeing temperature;
At 80⁰C, speed of diffusion of a dye in cellulose is higher than at 40⁰C.
Dyeing equilibrium is therefore achieved much more rapidly at 80⁰C than 40⁰C.

Temperature Substantivity

Subsantivity seems to be lower at

40⁰C than at 80 ⁰C, but in fact it is
not.
 Reactive dyes… Substantivity: Influencing parameters

Liquor ratio;

The Liquor ratio increases, the probability of contact between the dye molecules and the
fiber surface decreases.

Liquor ratio Substantivity

Don’t forget that the decrease is

also related to :

Dye concentration
Dye own affinity
So;
 Reactive dyes… Substantivity: Influencing parameters

Liquor ratio;

Dye concentration (L.R. 10:1=%100) Affinity of the dye

Dye :C.I. Reactive Red 180 Dye concentration :3%

Electrolyte :50 g/lt NaCl Electrolyte :50 g/lt NaCl
Dyeing temperature :40⁰C Dyeing temperature :40⁰C
 Reactive dyes… Substantivity: Influencing parameters

Fiber type;
Although the fiber structure has some minor effect on substantivity, we will see differences
e.g.; Mercerized cotton dyes to a much deeper shade than non-mercerized

It is merely the result of different optical properties: mercerized cotton has a circular cross
section,which allows better light penetration, less random light reflection.

Therefore, mercerized cotton can be much more easily penetrated by photons, thus a larger
proportion of coming light is selectively adsorbed and this means higher color saturation.
Raw cotton Mercerised and stretched cotton
 Reactive dyes… Diffusion rate: Influencing parameters

But fiber type has a significant effect on Diffusion Rate…

 Fiber type
 Dyeing temperature
 Size and shape of dye molecule
 Subsantivity of dye molecule
 Electrolyte concentration in the bath
 Dye concentration
Reactive dyes… Diffusion rate: Influencing parameters

Adsorption equilibrium diffusion

Dye uptake phase consist of successive

states of equilibrium.

Dye repeatedly makes

brief stops on the
crystallite walls

Diffusion rate of a dye , decides its

speed of exhaustion
Reactive dyes… Diffusion rate: Influencing parameters

So, speed of diffusion;

 Speed of exhaustion
 Levelness of dyeing
 Fixation
 Fastness properties
 Reactive dyes… Diffusion rate: Influencing parameters

Fiber type;
Cellulose Viscose Modal

Crystalline
regions

Such a large dye molecule can not diffuse into the Viscose is still stiff at 40-50⁰C, while at higher
highly oriented and tightly packed crystallites. temperatures (60-80⁰C ) the fibres mobility allows
Dyeing therefore proceeds at the outer walls . the fibre bundle open.
 Reactive dyes… Diffusion rate: Influencing parameters

When cotton is mercerized;

Fiber induces a higher orientation of crystallites, this should reduce the diffusion
rate but;

A large portion of of intermicellar spaces of the cotton is dissolved and extracted

by alkaline.
Large molecules can be penetrated more easily to the empty spaces so;

 Mercerized cotton swells dye more than non-mercerized

 Diffusion speed of a dye is much higher (Despite high orientation)
 Higher speed of exhaustion
 Stronger shade

Raw cotton Mercerized cotton

 Reactive dyes… Diffusion rate: Influencing parameters

Temperature;

Temperature Diffusion rate Temperature has by far the greatest

effect on diffusion

So greatest effect on;

 Migration rate
 Washing-off
 Levelness
 Reactive dyes… Diffusion rate: Influencing parameters

Size and shape of dye molecule;

Molecule size Diffusion rate

Larger and bulkier dye molecules have
a much slower rate of diffusion than
smaller ones
 Reactive dyes… Diffusion rate: Influencing parameters
Size and shape of dye molecule;
Reactive Blue 15 (Turquoise)

Reactive Red 198

>

MCT/VS
Bifunctional Reactive Dye
Phthalocyanine Poor;
Chromophore tents to  Diffusion
Diffusion rate:
be square and very  Levelling
Reactive Red 198 > Reactive Blue 15
bulk in the structure.  Washing-off properties
 Reactive dyes… Diffusion rate: Influencing parameters

Substantivity;
It promotes adsorption equilibrium but impairs diffusion speed.

High subsantivity dyes while exhausting more completely from the dye bath, diffuse,
migrate and level more slowly.
e.g.; Everzol Yellow LX
 Reactive dyes… Diffusion rate: Influencing parameters

Electrolyte concentration;

Electrolyte Conc. Subsantivity Diffusion rate

There is a small exception to this rule;

At very low electrolytes concentration adding a

trace of electrolytes to the dye bath helps to
improve diffusion.

This exception is rarely encountered in real-life

dyeing operation.
Reactive dyes… Fixation

T1: Addition of
alkali and start of
the fixation
Reactive dyes… Fixation

Alkali is necessary for;

 the dyestuff reaction with the fiber (heterocyclic type)

 formulation of reactive site and reaction of dyestuff with the cellulosic
fiber (vinylsulfone type)

Increasing alkali
………………………………
Decreasing reactivity

Soda ash
Soda ash/Caustic soda
Reactive dyes… Fixation

Then,
What is the meaning of heterocyclic or vinylsulfone…?
How is the reactive dyes chemical structure…?
Reactive dyes…
Fixation; Dye chemical structure

Chromophore Bridging RG
monofunctional

Reactive group

Functional groups ;
providing water solubility

conjugated
Chromophore Bridging RG RG
bifunctional

Bridging Bridging
isolated
RG Chromophore RG
bifunctional
 Reactive dyes…
Reactive group chemistry; Fixation; Dye chemical structure

Monochlortriazin (MCT) Monofluortriazine (MFT) Difluorochlorpyrimidine (FCP)

Cl
N rest N rest
F
N N N N
N N
Cl F F
•Low reactivity •Medium to high reactivity •High reactivity
•Sensitive to acid •Sensitive to acid •Stable to acid and alkaline
•Stable to alkaline •Stable alkali to alkaline •Splitting with peroxide and light
•May generate AOX •AOX free •AOX free

Vinyl sulfone (VS) Dichlorchinoxaline (DCC)

Chromophore
SO2-CH=CH2 N Cl

Bridge •Medium reactivity Cl

•Stable to acid N
•High reactivity
•Sensitive to alkaline
•Sensitive to acid
•Dischargeable, stripping is possible
•Not hydrolysable AOX
•AOX free
Increasing Reactivity
Reactive dyes… Fixation

Hot-dyeing dyes Cold-dyeing dyes

Substantivity

Everzol dyes

Reactivity
Reactive dyes… Fixation
Reactive dyes… Fixation

Everzol Yellow NPN Everzol Red LX

 Reactive dyes… Fixation

Dye-fiber reaction:

1. Nucleophilic substitution (MCT, FT, DFCT, DFP, DCQ, DCT)

A mobile halogen atom in the reactive group is substituted by the ionized nucleophilic
group of the cellulose.

Reactive Red 1
 Reactive dyes… Fixation

Dye-fiber reaction:

2. Nucleophilic addition

A proton and the ionized group of cellulose are added the active group of dye.

 In this example there is no bridging group

 The dyes react with cellulose by addition to
sulfur oxgen doble bond.

Reactive Blue 19
Reactive dyes… Fixation; influencing parameters

 Chromophore

 Reactivity of reactive groups

The more unstable the leaving group, the more reactive dye

 pH of the dyebath

With every increase bye one unit of the pH, the concentration of ionized nucleophilic
groups on cellulose increase, so the speed of reaction increase

 Temperature of the dyebath

 Substantivity of the dye

The reaction speed increasing as temperature rises and substantivity

 Reactive dyes… Fixation
Dye-fiber reaction:

Competitive reaction results; Inactivation of the reactive groups

N Cl + OH¯ N OH

N N N N
Cl OH

Dye-SO2- CH=CH3 + OH¯ Dye-SO2- CH=CH2CH2OH

 Reactive dyes… Fixation
Bireactivity and its consequences;
When considering:
A is a mono reactive dye with fixation of about 60%
B is a bireactive dye which have two reactive groups, each capable of achieving a
fixation of 60%

For B; fixed 84%

hydrolyzed 16%

For A: fixed 60%

hydrolysed 40%

Residue dyestuff (unfixed) in the dyebath

R-R can be either the same (homo-bireactive)
or different (hetero-bireactive)
 Reactive dyes… Fixation
Bireactivity and its consequences;
Skillful combination of two different reactive groups can ensure elimination of each
group’s spesific fastness weakness.

MCT; stable to alkali

VS; stable to acid By comparison to

monofunctional dyes;

 more stable dye/fiber

bond to acid and alkali
 a longer shelf life
 much better chemical
stability
Reactive dyes… Washing

T1: Addition of
alkali and start of
the fixation
Reactive dyes… Washing
Dyed
fiber

Washing

Value-Adding

Less Effluent
Fixed dye molecules
Unfixed dye molecules Easy Wash-Off
Chemicals
 Reactive dyes… Washing

As a general rule of thumb;

The best results are obtained if washing off is carried out;

Substantivity of the dye is as low as possible and diffusion rate as high as possible.

-at high temperatures

-with lowest possible electrolytes conc.
-at higher liquor ratio

to reduce the affinity/substantivity

of dye molecules to fiber
 Reactive dyes… Washing

30⁰C 60 ⁰C 98 ⁰C 80 ⁰C 60 ⁰C 30 ⁰C

Dye with low affinity and good diffusion;

Most of dye extracted cold, which shows that it was only adhering to the fibre surface.
An insignificant amount of unfixed dye remains inside the fiber matrix.
Reactive dyes… Fastness of reactive dyes

Wash Fastness
Light Fastness
Detergent, heat, water
water & light
perspiration & light

Reactive
Chromophore -N=N- anchor Fiber

Heat
Bleaching Fastness
Acid
Chlorine Alkali
Peroxide
Reactive dyes… Fastness of reactive dyes

Wash Fastness

Problems may result from;

1. uncomplate washed off hydrolyzed dyestuff

2. washing conditions which destroy the Chromophore e.g. washing

detergents with bleaching agents

3. conditions which split the dyestuff-fibre bond

Light Fastness

Highly dependent on chromophore Reactive

Chromophore Fiber
anchor
Reactive dyes… Fastness of reactive dyes

Bleaching Fastness

1. Strong dependent on chromophor

2. Chromophore class is important with pattern on substituent adjacent to the azo

group

3. Even similar elements in the chemical structure big differences in chlorinated and
bleaching fastness

Oxidation agent

Reactive
Chromophore Fiber
anchor
 Reactive dyes… Fastness of reactive dyes

Rubbing Fastness

 Material
 Construction of material (knitted, textured..)
 Dye (molecule size, chemistry…)
 Dyeing method
 Washing
 Finishing
 Wet/dry rubbing
Reactive dyes… Fastness of reactive dyes

Cotton; Cotton;
Raw material Dyeing reactive dyes, than wet rubbing
Reactive dyes… Fastness of reactive dyes

Viscose; Viscose;
Raw material Dyeing reactive dyes, than wet rubbing
Reactive dyes… Hints

The molecules of most colored organic compounds

contain two parts:

i) An aromatic ring such as benzene, naphthalene or

anthrhracene

ii) Conjuge double bond system containing unsaturated

groups

The intensity of color can be increased in a dye molecule

by addition of substituents;
 Reactive dyes… Hints

For Printers…

Pint-paste is should be stable several days without any noticeable inactivation (hydrolysis)
of the reactive dye. MCT reactive groups are suitable with;

 Hydrolyze slowly at room temperature

 Fix rapidly under the usual steaming conditions.

For Viscose…

MCT is a good choice when dyeing viscose by the exhaust method at 80°C .

The higher temperature reduces the risk of poor levelness because:

 The swollen viscose is more accessible to the dyebath than at lower temperatures
and the dye more evenly distributed in the material.
 The levelling effect of dye diffusion is more effective at high temperatures.
Reactive dyes… Hints

For Cold Pad-Batch dyers…

Prefer dyes that are;

 completely fixed at room temperature at (pH: 11.5-12.5)
 To be resistant to hydrolyze

these conditions are met for example by VS, MFT, DFP or DFCP bireactive dyes
which combining two reactive groups of similar, medium reactivity.
Reactive dyes… Exhaust dyeing method